1. Technical Field
The present disclosure relates to apparatus and methods for alignment and height sensing.
2. Description of the Background Art
A conventional lithographic process includes the patterned exposure of a resist allowing portions of the resist to be selectively removed, thereby exposing underlying areas for selective processing, such as etching, material deposition, ion implantation and the like. Typically, lithographic processes utilize ultraviolet light for selective exposure of the resist.
In addition, charged particle beams (e.g., electron beams) have been used for high resolution lithographic resist exposure. The use of e-beam based lithography systems allows for relatively accurate control of the electron beam at relatively low power and relatively high speed. Electron beam lithographic systems may include electron-beam direct write (EBDW) lithography systems and electron beam projection lithography systems.